After an integrated circuit (IC) is manufactured, it must be tested to ensure that it functions properly. Scan testing can be an efficient method for determining which portions of an IC are working properly. ICs are generally tested by providing known patterns to particular inputs of the IC and analyzing the resultant outputs from the IC. If the IC provides the proper outputs in response to the provided inputs, the manufacturer is assured that the IC is working properly.
The insertion of test points within an IC may assist in improving the testability of ICs that are difficult to test, and may reduce the number of test patterns and test time required. There are two basic types of test points that are used in IC testing: control test points (CTPs) and observe test points (OTPs). Control test points may be used to make a difficult to control circuit node more easily controllable and observe test points may be used to make a difficult to observe node easier to observe by adding additional logic to the design. Control test points may also add performance overhead to the design.